Dear, these days I'm facing on several motor vibration problem. This is one of them. I want to hear your opinions.
the motors vibration amplitude for multi stage pumps was raised up from 3 to 9 mm/sec RMS for this year.
On the FFT, 1X horizontal vibration is dominant about 90% of overall value. And this motor vibration is transferred to motor base - foundation - concrete floor and near same machine motor that is still power off but vibration is about 1 ~ 1.5 mm/sec.
Is it motor unbalance problem? already motor overhauled and checked weight balance.
Is this vibration was effected due to motor base plate stiffness? Motor base was fabricated channel looks like weak for this heavy motor. But 9 month ago vibration was not high like recent and there is no evidence of base crack for welding point.
Is this vibration was effected due to electrical things? Why does power off motor have vibration?
( Motor : 337kW, 2P, 6600V, 60Hz, 2450Kg, Bearings 6218C3)